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Subject[patch 05/24] x86_64: Fix a race in the free_iommu path.
-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Mike Waychison <mikew@google.com>

We do this by removing a micro-optimization that tries to avoid grabbing
the iommu_bitmap_lock spinlock and using a bus-locked operation.

This still races with other simultaneous alloc_iommu or free_iommu(size
> 1) which both use bus-unlocked operations.

The end result of this race is eventually ending
up with an iommu_gart_bitmap that has bits errornously set all over,
making large contiguous iommu space allocations fail with 'PCI-DMA:
Out of IOMMU space'.

Signed-off-by: Mike Waychison <mikew@google.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86_64/kernel/pci-gart.c | 4 ----
1 file changed, 4 deletions(-)

--- linux-2.6.16.11.orig/arch/x86_64/kernel/pci-gart.c
+++ linux-2.6.16.11/arch/x86_64/kernel/pci-gart.c
@@ -114,10 +114,6 @@ static unsigned long alloc_iommu(int siz
static void free_iommu(unsigned long offset, int size)
{
unsigned long flags;
- if (size == 1) {
- clear_bit(offset, iommu_gart_bitmap);
- return;
- }
spin_lock_irqsave(&iommu_bitmap_lock, flags);
__clear_bit_string(iommu_gart_bitmap, offset, size);
spin_unlock_irqrestore(&iommu_bitmap_lock, flags);
--
-
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